Allen-Bradley PLC-5 User Manual page 231

Waiting State
While block-transfer to remote rack
occurs, a rescheduling operation is
performed and lower-priority programs
are executed (unless all other
executions are prohibited by a UID/UIE
zone around the block-transfer.
Completed State
Program has completed execution
or has not yet started execution
Ready State
Program would be executing if it were of a higher priority;
all programs pass through this state; there can be
several programs in this state at any given time
Waiting State
Program is ready for execution but is waiting
for some event to occur (such as an input to
transition or a timer to complete)
Executing State
Program is executing; only
one program can be in this
state at one time
Has a new program
with a higher priority
become ready?
(e.g., an MCP, STI, PII)
Does the program fault?
Yes
Does the program request
a remote block transfer?
(STI and PII routines only)
Completed State
Program has completed execution
or has not yet started execution
Yes
No
Yes
No
Does an appropriate fault routine
No
are aborted and processor
Programming Considerations
Faulted State
A run-time error
has occurred within
the program
Program counter is
adjusted to point to
next instruction
choose to clear the fault?
No
All active user programs
enters faulted state
Publication 1785-UM012D-EN-P - July 2005
13-13
Yes